LeetCode 解题报告 Binary Tree Preorder Traversal

Given a binary tree, return the preorder traversal of its nodes' values.

For example:

Given binary tree

{1,#,2,3}

,

1
\
2
/
3

return

[1,2,3]

.

分析：

同样也是用栈来进行存储

/**
* Definition for binary tree
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public List<Integer> preorderTraversal(TreeNode root) {
List<Integer> result = new ArrayList<Integer>();
Stack<TreeNode> stack = new Stack<TreeNode>();
TreeNode node = root;
if(node != null)
stack.push(node);
while(!stack.isEmpty()){
node = stack.peek();
stack.pop();
result.add(node.val);

if(node.right != null)
stack.push(node.right);
if(node.left != null)
stack.push(node.left);
}
return result;
}
}